Motor runs when wired direct to door switch, would it be the relay or the control board? How could I figure out which Thanks

Post the make and model of the cicuit board.


Usually the relay and timers controlling the fan motor are part of the circuit board.

Does the wiring to the fan motor connect to a relay or to the circuit board?

Is your furnace going out on high limit (burners ignite, but then go out a minute or two later because the blower isn't kicking in? Can you let us know exactly what is happening with the unit when there is a call for heat.

As SP suggested, most likely your fan relay is part of the control board. And if fualty, you would need a complete new board. But don't go buying a board just yet, let us know a little more about the problem and we will do our best to verify.

Thanks for your help guys, the burners ignite for a minute or two and then go out with the light giving four blinks. Tha blower never comes on. The board is a PCBBF1325 . I plugged the Cool wire from the board,into the door wire and the blower actually ran. Thanks

All the wires from the fan motor go into the circuit board which I believe is an Emerson make. The outside compressor runs and pumps cold freon but the blower won't come on for the AC either.

Okay, four blinks on your furnace does indicate an open limit. The open limit (in your case) is mostly because the blower isn't kicking in, so the furnace "overheats". Now, you say you powered the cool (black wire) and the fan ran? What about the red, yellow, blue. If you power them, does the fan still run? If so, it really looks like you need a new control board.

Just know that I hate recommending replacing a main board without knowing for sure that that is the problem. But without being there to test things for myself, and judging from the info you have given, I lean strongly towards a new board. Good luck and please let us know how things work out.

Fan blower worked in cool AND heat modes when wired direct. Local dealers were prohibitively expensive so I went to internet and found a new control board at HVAC Parts Outlet for $69.99 plus nominal shipping. Board arrived today and it's functioning perfect through thermostat for heat and cool. Thanks guys for your help!

Thanks for the update, glad you got it fixed.

For the shipping interval, I made a 2 way splitter , one end to the board "cool" and the other two to the door cut-off wire and the Fan Cool blower wire respectively and thus was able to have the unit work ( Cool AND Heat)via the house outlet plug with the fan on continuously , un-plugging it when the desired temp. was reached. Not really recommended, but under close supervision, it worked. I hope I can at the very least be a little help. Thanks again